The present invention relates in general to universal joints and in particular to an improved seal and dust guard assembly for use with a bearing cup mounted on a trunnion of a universal joint cross member.
Universal joints are structures which are well known in the art. Such joints usually include a cross member having a central body portion with four trunnions extending outwardly therefrom. The trunnions extend at right angles relative to one another and lie in a single plane. A hollow cylindrical bearing cup, closed at one end, is disposed over the end of each of the trunnions. Roller bearings are provided between each of the bearing cups and its associated trunnion such that the bearing cups are rotatably mounted thereon. Lubricant can be injected into the cross member through a fitting secured in an aperture formed through the body portion. The aperture communicates with respective passageways formed through each of the trunnions. Such injection, commonly referred to as purging, forces the lubricant outwardly from the body portion through the trunnions toward the closed ends of the bearing cups. The lubricant passes around the outer ends of the trunnions adjacent the closed ends of the bearing cups and radially inwardly back between the bearing cups and the trunnions where the roller bearings are disposed. In this manner, the roller bearings are lubricated for use.
It is known to attach a metallic dust guard to each of the trunnions in order to prevent the entry of dirt or other contaminants into the regions of the cross member where the roller bearings are located. Additionally, it is known to provide the open ends of the bearing cups with elastomeric seals. Such seals also prevent the entry of contaminants into the cross members, and further restrict the flow of lubricant out of the region of the cross member where the roller bearings are located. In prior art cross members, it has been found that these elastomeric seals did not consistently provide a uniform sealing pressure against their associated trunnions. This non-uniform sealing pressure occurred because the dust guards were vulnerable to being nicked or dented during the assembly of the cross member into the end yokes of the universal joint. Such deformation of the dust guard occasionally caused it to contact the seal, resulting in a variance in the degree of sealing pressure applied by the elastomeric seal against the trunnion near such point of contact. In this situation, non-uniform lubricant injection resulted throughout the cross member during the purging process, since most of the lubricant flowed through those seals which applied less pressure against the trunnions, while little lubricant flowed through those seals which applied greater pressure. Obviously, this undesirable situation could result in one or more of the trunnions being inadequately lubricated.